This invention relates generally to imaging systems, and more particularly, to nuclear medicine imaging systems having pixelated detectors.
Nuclear medicine imaging systems, for example, Single Photon Emission Computed Tomography (SPECT), Computed Tomography (CT) and Positron Emission Tomography (PET) imaging systems, use several image detectors, such as one, two or three detectors, to acquire imaging data, such as gamma ray or photon imaging data. The image detectors may be, for example, gamma cameras that acquire two-dimensional views of three-dimensional distributions of radionuclides emitted from an object (e.g., a patient) being imaged. The image detectors may be rotated about a patient to acquire a plurality of two-dimensional images (also referred to as projections) to create a multi-dimensional image of a structure of interest or photons transmitted through the object. These rotating nuclear medicine systems are referred to as single photon emission computed tomography (SPECT) imaging systems. In SPECT systems, 40, 60 or more projections may be acquired, which are then reconstructed to generate a three-dimensional dataset. Iterative reconstruction algorithms known in the art may then use information about the physical construction and properties of the imaging system to reconstruct the dataset into three-dimensional and/or four-dimensional representations. The three-dimensional or four-dimensional dataset then may be used to show different slices along or regions within the dataset and display the results as an image similar to images obtained from other tomographic imaging scans, such as, magnetic resonance imaging (MRI) and computed-tomography (CT) scans.
Gamma cameras for detecting photons for SPECT, PET, CT, etc. are often fabricated from semiconductor materials, such as cadmium zinc telluride (CdZnTe), often referred to as CZT, cadmium telluride (CdTe), gallium arsenide (GaAs) and silicon (Si), among others. These semiconductor gamma cameras typically include arrays of pixelated detectors or detector modules. In these pixelated detectors, individual or groups of pixels that are not operating properly, either continuously or intermittently, can cause significant problems during image reconstruction. For example, one or more detector pixels may be incorrectly adding photon counts such that photon count data from those detector pixels improperly dominates the image reconstruction process. The one or more detector pixels that are not operating properly can cause significant image artifacts, thereby decreasing image quality and reducing the reliability of the results and any analysis of the images. In order to address the problem with the pixels in the detector that are not operating properly, the entire detector may have to be replaced at a very high cost.